Downdraft carburetor



July-21, 1931.

R. M. ANDERSON novmmpr cmsmmo Filed ay o. 1929 2 Shouts-Sheet 1 'RAYMOND MANDER Q ame/ntm:

July 21, 1931. R. M. ANDERSON DOWNDRA FT CARBURETOR N ou (St 2 n E m w m M D N O. M v 1 .A m u R 1 .o O l x w M d e u F a I me aa Juli 21, 1931 'UNITEDSTATES PATENT OFFICE' Immom) it.- ANnEBsoN, or

DowmmAFT Application mea ay 10,

` This invention refers specifically means for accelerating the throttle is opened. v

' Fig. 1 showsdiagrammatically allthe essential elements of the carburetor. I I Fig. 2 shows a detail elevation of the throttle control.

I Fig. 3 is a plan view 'ments of the' parte.

In Fig. 1, A is the air entrance, B is the throttle valve located 'in mixture outlet L and %peratin a ratchet C through a spur wheel see ig. 2) .which raises and lowers, by 'means of the bracket M, the needle valve D fuel supply when the showing the ari-angechamber E through a passage F.

The flow through F is also controlled by the float valve K' controlled by the float K. This float is enclosed in a special auxiliary float chamber H, the upper part of which has a vent J controlled 'by the float valve K' which is fol-med on the upper end of the float valve K'. The chamber H is also vented at K to the fioat chamber E which is vented at E to the atmosphere. An overflow E is also provided The fuel level in E is maintained at XX by the conventional'float mechanism G. The fuel nozzle N forms the outlet from the passage F controlled by the needle valve D and is located below XX and discharges into the throat Y of the mixing chamber which is of Venturi form. ;Concentric with N is the passage O so that a small annular passage is i communicates with the vertical passage P which communicates with the mixture outlet L through the ;restricted outlet P; The vent J of the smaller auxiliary float chamber H communicates through passages S,"S', S and S withthe passage P for the 'purpose to be described later. e

The fuel pump shown in Fig. 1 'comprises a cylinder U with skir't depending below the level XX in the float chamber and a piston W which slides freely within the c linder U is provided. The piston W is a apted to be raised by the hook link V attached to the plate M andtodescend under its own' weight.

connected to the end of the hook valve V DETROIT, MICHIGAN, ASSIGNOB 'ro or person MIEIGAN which Controls the fuel flowing from the fl'oat l formed between N and O. This passage O? GEQME M. HOLLEY;

camumroa' 12529. Serial No. 361942.

'T leading out of the upper part of.the cylinder U is a check valve Z. The fuel outlet T discharges into the air entrance A.

e j An air chamber. Z' is provided in the u pe wall of thefloat chamber having a restricted communication with the nozzle T for a purpose to be described. The discharge'bitlet from T is restricted as shown at i The piston W is preferably made of soine material such as Invar which has a' low coefficient of expansion, lower than that of the cylinder U, -which may be made of brass,

aluminum or bakelite.

' When the engine to which the carburetor is attached is started, a. suflicient depression is created in the m'xture outlet L to cause the air in the upper part of the auxilary float chamber H to flow through J and the passages S', 8 and S to the mixture outlet passage P, P'. The float K' is thereby 'raised-thus opening the valve K' 'and closng the valve K'. The fuel then flows by gravty from E throu h F to nozzle N where some of the fuel ows around the nozzle N through the passage O to the passage P and so issues at the point P'` into the mixture outlet L. This arrangement insures steady silent idle runnn v O n opening the throttle the depression at O and also' Y increases just as the depression at L and P'- decreas'es so that at all times there is-a de ression in H suflicient to cause thevalve to open the fuel outlet. When the throttle is open the rack C and the pinion C' raises the bracket Mand thereby raises the needle valve D which regulates the flow of 'fuel through F to N. On suddenly opening noted that repeated openings ofthe throttle in quick succession will not cause an eXcessive amount of fuel to be pumped into the air entrance because' the piston W can only return as fast as gravity 'will permit.

Owing to the difierence in coefficients of eX- pansion of the materials of which the cylinder U and the pston W are made, the efiectiveness of the pump depends upon the temperature. At relatively high temperatures, for example, higher than F., the clearance between the pisten W and the cylinder U becomes so great that a considerable portion of the fuel displaced by the pston XV le aks back into the fioat chamber E and the pump thereby becomes less effective It will be noted that the fuel for acceleration enters into the air entrance above the mixing chanber through which it flows by gravity on to the throttle.

hat I claim is:

1. In a' carbureter having a throttle valve, accelerating means comprising a throttle operated pump, a cylinder made from mate'- rial having a relatively high coefiicient of eX- pansion, a piston made from a metal having a relatively low coeflicient expansion, said piston being adapted to be operated by said throttle.

2. In a carburetor having a constant level fuel supply chamber, a fuel nozzle fed therefrom, a mixing chamber, a throttle valve, acceleratng means comprsing an open ended inverted cylinder having its skirt depending below the level in said supply chamber, a piston slidable therein and having an opening therethrough, a valve 'engagng with the under side of said piston and adapted to sealsaid opening, link means connecting said valve with said throttle whereby the piston is raised when the throttle is opened, a fuel outlet from said cylinder, a check valve in said outlet, and a passage from said outlet to said mixing chamberj 3. In a cafburetor having an air entrance and -a throttle valve, acceleratng f'el supply means comprising a cylinder, a pist'on theren adapted to be operated by said throttle, a fuel entrance to said cylinde'r controlled by said throttle, a fuel outlet from said cylinder, a check valve in said outlet, a restricted fuel nozzle discharging into said oarburetor air entrance, a passage connecting said fuel nozzle and the outlet from said cylnder, a closed air chamber communicating with said passage for the purpose described.

In testimony whereof he aflixes his signature. a

RAYMOND M. ANDERSO N. 

